Knife-edge light stop for microscopes



Jan. 9, 1951 w. F. MUNN v 2,537,846

KNIFE-EDGE LIGHT STOP FOR MICROSCOPES Filed June 25, 1947 nventorgua/M37 MfaAM.,

(Ittornegs Patented Jan. 9, 1951 UNITED STATES PATENT OFFICE KNIFE-EDGELIGHT STOP FOR MICROSCOPES 7 Claims.

This invention relates to optical devices and, more particularly, to anattachment for a system of lenses, e. g. a microscope.

In many optical devices, particularly those such as cameras, telescopesand compound micros copes (hereinafter referred to as microscopes) wherean image is formed through a single system of lenses, there is nobinocular effect and the sense of depth in the image formed is 'lost toa Very marked extent. ',Ihis sense of depth may be somewhat restored ina microscope by illuminating the object with light falling thereon at anangle to the axis of the microscope rather than axially thereof so as toproduce light and Yshadows on the object, thus creating to some degreean eifect of depth. An effect of depth is very important in obtainingclear images, disclosing the true na ture of the object being studied,whether for direct observation or for microphotographs.

In the form of the present invention shown, a knife edge has been placedat a principal focus of the eyepiece lens or lens system of a microscopeand introduced from one side into the image-forming light passingthrough such lens a sufficient distance to intercept some of the" light.,The effect of this interception is somewhat similar, but superior tothat obtained from oblique lighting of the object but is accomplishedwith the normal axial lighting of the object. As the knife is slowlymoved tointercept the image-forming light rays, it will be noted that,at a certain point in the knifes movement, a very marked effect of depthoccurs in the image formed by the microscope, crystals or transparentbers standing out in relief in the image so as to be readily observablein detail. The attachment to be described isadaptable for application toany microscope or similar system of lenses and, upon modification, canbe applied to other lens systems. An object of the present invention Visto im- Y prove the image formed from a microscope or other lens system.

Another object of the invention is to obtain in a'microscope or otherlens system an improved three-dimensional effect, or effect of depth, soi:

as to obtain greater detail in the image formed.

I Further objects and objects relating to details and economies ofconstruction will more dennitely appear from the detaileddescription tofollow.

My invention is clearly defined in the appended claims. Where parts are,for clarity and convenience, referred to on the basis of their orientedposition shown in the accompanying drawing, no limitation as topositioning of the entire structure is to be implied, since it will beunderstood that the entire structure can be inverted,l

and that it can be used in an inclined position. Also in both thedescription and the claims, parts at times may be identified by specicnames for clarity and convenience, but such -nomenclature is to beunderstood as having the broadest vmeaning consistent with the contextand with the concept of my invention as distinguished from the pertinentprior art. The best form in which I have contemplated applying myinvention is illustrated in the accompanying drawing forming part ofthis specification, in which Fig. 1 is a diagrammatic View of amicroscope incorporating the present invention.

Fig. 2 is an elevation, on an enlarged scale, of the top and eyepieceportion of a microscope, including an elevation of the image-improvingattachment.

Fig. 3 is a top plan view of the portion of the microscope and theattachment shown inFig. 2.

Referring to the drawings, my attachment may be placed on a conventionalmicroscope I0. This microscope, which is indicated diagrammatically inFig. l, is provided with an object slide I I which is illuminated in theconventional manner by axial light rays i2 passing through a series oflenses forming a light condenser I4. The matter to be examined ismounted on the slide II in usual fashion; and the light from the slideis transmittedthrough an object lens I5 which may, and usually does,comprise a series of individual lenses.

The light from the slide iI, after passing through the object lens EE,passes upwardly axially of the microscope and through an eyepiece lensi5, as is well-known. The eyepiece lens IE5 likewise is usuallycomprised of several individual lenses. The distance of the eyepiecelens i3 from the object lens I5 is adjusted by mounting the eyepiecelens in the upper end of an eyepiece or tube E? which is teiescopableaxially of the main tube I9 of the microscope.

rSine image is observed by placing the eye of the observer somewhatabove` the yeyepiece lens IE. If a permanent record is to be made of theimage Vformed in the microscope lil, a camera may be positioned over theeyepiece lens IS .in place of the observers eye to take a picture orphotomicrograp-h oi the image formed in the micrcscope IS. The foregoingform of microscope is conventional and well-known.

i have found that the image formed by a microscope may be greatlyimproved by placinga knife edge 2 in the image-forming light rays at theprincipal focus F of the eyepiece lens I6 above the lens. The knife edgeis preferably formed. as a straight yedge from a thin flat strip ofmetal and positioned in a plane at right angles to the axis of themicroscope. Since the eye of an observer is placed above the principalfocus F' of the eyepiece lens I6, the knife edge 20 does not interferewith observation of an image in the microscope.`

I have found that as' the knife edge 20 is slowly moved from one side ofthe axis of the microscope I0 to partially intercept the imageformingrays of light passing through the eyepiece lens I6, the image formed bythe microscope is suddenly improved. While previously the image had hadlittle or no'appearance of depth, the image at once takes on an effectof depth or relief which is not ordinarilyy obtainable without binocularvision. It appears as though crystals or membranes o'f the object castshadows, thusA permitting and. facilitating a closer study offtheobjectbeing examined. This effect is.. somewhatl analogous but'y vastlysuperior to thatlobtained by oblique. illumination of the objectslideI'I.`

Thephenomenon above described occurs when theknife edgelii. isiplaced'soas to intercept only aportion oflthe-image-forming light rays fromasingle side of the eyepiece lens I6'. There is a certain optimumposition ofthe knife edge in which. therelief effect is obtained but theentire fieldlis notnoticeably darkened. This position is conveniently:obtained by slowly advancing the k-nifeedge 2U toward.. the axisof themicroscope at the principal: focusF of the eyepiece lens I6 l whileobserving the image. A' rather exact adjustment ofthe knife edgev 20. isrequired to obtainthe.abovedescribed`effect to best advantage.

If the knife edgelll. is appreciably above or below:the principal focusF of the eyepiece lens |6,.a definite darkening of only a. portion ofthe 'eldresults andnofrelief effect is obtained. This darkening isonthesidetoward or away from the knife edge,. depending. upon whetherthe knife ed'ge20is aboveor below the. principal focus respectively,ofthe eyepiece lens I6.

Atthe same time that the relief or depth effeetofthe image formed by themicroscope l) is-.improved'by interpositioning of the knife edge Zil,one side only of the field of view is slightly darkened but the entirefield is not so darkened. The darkened side of Vthe field of view isopposite to that on which the knife edge 2i) is introduced. For thisreason, I prefer to introduce the knife edge 2U into the image-forminglight rays from the side opposite to that of the observer, thus throwingthe shadows of the relief image toward the observer so as to obtain animage to which the human eye is more accustomed.

I am unable to explain the physical phenomena above described butbelieve it to be due in some manner to diffraction due to partialinterception of the image-forming light rays at a principal focus of theeyepiece lens i6. I have determined that if the.image-forminglight.raysare symmetrically intercepted at the principal` focus of the eyepiecelens, the' entire field is. darkened equally and no relief or deptheffect is obtained. However, it is not essential that a knife edge beernployed, since I have obtained ycomparable results with a iiat opaquemember having a straight edge of substantial thickness which is movedinto the image-forming rays'at the focus of the eyepiecev lens.

Referring to Fig. 2, my microscope attachment preferably includes around upright post 2| secured to the microscope beside the eyepiece lensI6 by a split ring 22 clamped about the eyepiece Il by a screw 24. Thepost 2| receives a slide 25 having two spaced holes, the slide beingvcapable both of rotation and reciprocation on vthe post. A leaf spring26 is secured to the slide 25 andy bears against the `post 2I to causethe slide. to: frictionally engage. the post andremain in any setposition.

The knife edge 20 may be mounted directly on the slide 25. It may beformed of a flat piece of steel having a straight thin edge and mountedin a plane perpendicular to the axis of the microscope. Preferably itdoes not extend far beyond the periphery of the eyepiece Il to permitthe'hood of a'camera to be passed about the eyepiece when making aphotomicrograph.

The above-described mounting for the knife edge 20 serves asa readymeans for positioning it at the level of the .principal focus F aboveAthe eyepiece'lens I B and for adjustingvr it'into the` image-forming.light` rays to obtain the'l best' image ofthe object being'studied, asabove described.

This attachment can also be usedwithout modi- 'cation when using 'themicroscopein the'taking' of photomicrographs.` In such case the'micro'escope is adjusted, including adjustment of the knife edge 2i! to securethe best image'. A suitable camera, not shown,.is thenlpositioned'abovethe microscope inthe. conventional manner toY take the photomicrographs.

I claim:

1. In a compound. microscope for viewingror` photographing an object ormaterial mounted Yon a-conventional slidethe microscope havinganobjective lens and an eyepiece lens formed of vat least two individuallenses,. the improvement which comprises: a member disposable at thevprincipal focus and beyond said'eyepiecelenslin they optical system and.unsymmetrically ofthe axis of.. the eyepiece lensto intercept aportion:

of the image-formingzlight passing` therethrough.

2. In a compo-und microscope` for viewing, or'

photographing an object or material mountedon a conventional slide, themicroscope having an objective lens and aneyepiece lens formed ofl atVleast two' individual lenses, the improvement which comprises: 'a thinflat knife edge positionable above` said eyepiece lens at the principal.focus thereofto intercept unsymmetricallyvrelative to the axis` thereofimage-forming light passing through said eyepiece'lens.'

3. In a compound microscope for viewingor photographing an" object ormaterial mountedon a conventional slide, the microscope having-anobjective lens' and-an eyepiece lens` formed vofv at'` least twoindividual' lenses, the improvement which-comprises: a thin, flat knifeedge sup'- ported at the principal focus and'beyond 'said eyepiece lensin the opticalf system, andmeans for adjusting said knife edge tounsymrnetrically intercept' image-forming light passing through4 saideyepiece lens:

4. In a' compound' microscope for viewing or photographing an object ormaterial mounted on a conventional slide, the microscope havinganobjective lens and an eyepiece lens formed of at least" two individuallenses, the improvement which comprises: a thin, at knife edge supportedfor movement in a planeperpendicularto the axis of said eyepiecel lensat the principal focus beyond said lens in the optical system, and meansfor adjusting said knife edge to unsymmetrically intercept image-forminglight passing through said eyepiece lens.

5. In a compound microscope for viewing or photographing an object ormaterial mounted on a conventional slide, the miscroscope having anobjective lens and an eyepiece lens formed of at least two individuallenses, the improvement which comprises: a thin, flat knife edgesupported for movement in a plane perpendicular to the axis of saideyepiece lens at the principal focus ben yond said lens in the opticalsystem, and a stationary post and slide rotatably mounted on said postfor adjustably mounting said knife edge.

6. In a compound microscope for viewing or photographing an object ormaterial mounted on a conventional slide, the microscope having anobjective lens and an eyepiece lens formed of at least two individuallenses, the improvement which comprises: a thin flat knife edgesupported for movement in a plane perpendicular to the axis of saideyepiece lens at the principal focus beyond said lens in the opticalsystem, a round stationary post mounted on the eyepiece parallel to theaxis of the miscroscope, and a slide rotatably and reciprocably mountedon said post and frictionally engaging said post and mounting said knifeedge, the frictional engagement of said slide maintaining the knife`edgein adjusted position.

7. In a microscope for Viewing or photographing an object or materialmounted on a conventional slide, the microscope having an objective lensand an eyepiece lens formed of at least two individual lenses, theimprovement which comprises: a thin, flat knife edge movable in a planeperpendicular to the axis of said eyepiece lens at the principal focusbeyond the eyepiece lens in the optical system, a round stationary postmounted on `the eyepiece parallel to the axis of the microscope, a sliderotatably and reciprocably mounted on said post, and a member attachedto the slide and resiliently engaging the post to retain the slide inadjusted position, the knife edge being mounted on the slide.

WILLIAM FAITOUTE MUNN.

REFERENCES CETED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS OTHER REFERENCES Bell: The Telescope, 1st edition,page 212, published by McGraw-Hill Book Co., Inc., New York city, 1922.

Edser: Light for Students, pages 98-99, published by MacMillan & Co.,Ltd., London, 1944.

Strong: Procedures in Experimental Physics, pages 69 to 72, published byPrentiss-I-Iall, Inc., New York city, 1946.

